Pose Mode: How to reset transformed armature to its rest position?
Select all the bones, in pose mode with A. Then, hit:

ALT R to reset all rotations,
ALT G to reset all translations,
ALT S to reset all scales.

Or, you can select all bones (A) and hit space. Then search for &quot;clear pose&quot; and select Clear Pose Transforms in the results. Et voilà!
Mac Users Use Option instead of ALT.